373 lines
9.2 KiB
Rust
373 lines
9.2 KiB
Rust
#[doc = "Operations and constants for `float`"];
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// Even though this module exports everything defined in it,
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// because it contains re-exports, we also have to explicitly
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// export locally defined things. That's a bit annoying.
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export to_str_common, to_str_exact, to_str, from_str;
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export add, sub, mul, div, rem, lt, le, gt, eq, eq, ne;
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export is_positive, is_negative, is_nonpositive, is_nonnegative;
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export is_zero, is_infinite, is_finite;
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export NaN, is_NaN, infinity, neg_infinity;
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export consts;
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export logarithm;
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export acos, asin, atan, atan2, cbrt, ceil, copysign, cos, cosh, floor;
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export erf, erfc, exp, expm1, exp2, abs, abs_sub;
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export mul_add, fmax, fmin, nextafter, frexp, hypot, ldexp;
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export lgamma, ln, log_radix, ln1p, log10, log2, ilog_radix;
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export modf, pow, round, sin, sinh, sqrt, tan, tanh, tgamma, trunc;
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export signbit;
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export pow_with_uint;
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// export when m_float == c_double
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export j0, j1, jn, y0, y1, yn;
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// PORT this must match in width according to architecture
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import m_float = f64;
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import f64::*;
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/**
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* Section: String Conversions
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*/
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#[doc = "
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Converts a float to a string
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# Arguments
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* num - The float value
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* digits - The number of significant digits
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* exact - Whether to enforce the exact number of significant digits
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"]
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fn to_str_common(num: float, digits: uint, exact: bool) -> str {
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if is_NaN(num) { ret "NaN"; }
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let mut (num, accum) = if num < 0.0 { (-num, "-") } else { (num, "") };
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let trunc = num as uint;
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let mut frac = num - (trunc as float);
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accum += uint::str(trunc);
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if (frac < epsilon && !exact) || digits == 0u { ret accum; }
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accum += ".";
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let mut i = digits;
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let mut epsilon = 1. / pow_with_uint(10u, i);
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while i > 0u && (frac >= epsilon || exact) {
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frac *= 10.0;
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epsilon *= 10.0;
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let digit = frac as uint;
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accum += uint::str(digit);
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frac -= digit as float;
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i -= 1u;
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}
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ret accum;
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}
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#[doc = "
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Converts a float to a string with exactly the number of
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provided significant digits
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# Arguments
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* num - The float value
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* digits - The number of significant digits
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"]
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fn to_str_exact(num: float, digits: uint) -> str {
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to_str_common(num, digits, true)
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}
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#[test]
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fn test_to_str_exact_do_decimal() {
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let s = to_str_exact(5.0, 4u);
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assert s == "5.0000";
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}
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#[doc = "
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Converts a float to a string with a maximum number of
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significant digits
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# Arguments
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* num - The float value
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* digits - The number of significant digits
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"]
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fn to_str(num: float, digits: uint) -> str {
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to_str_common(num, digits, false)
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}
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#[doc = "
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Convert a string to a float
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This function accepts strings such as
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* '3.14'
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* '+3.14', equivalent to '3.14'
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* '-3.14'
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* '2.5E10', or equivalently, '2.5e10'
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* '2.5E-10'
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* '', or, equivalently, '.' (understood as 0)
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* '5.'
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* '.5', or, equivalently, '0.5'
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Leading and trailing whitespace are ignored.
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# Arguments
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* num - A string
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# Return value
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`none` if the string did not represent a valid number. Otherwise, `some(n)`
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where `n` is the floating-point number represented by `[num]`.
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"]
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fn from_str(num: str) -> option<float> {
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let mut pos = 0u; //Current byte position in the string.
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//Used to walk the string in O(n).
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let len = str::len(num); //Length of the string, in bytes.
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if len == 0u { ret none; }
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let mut total = 0f; //Accumulated result
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let mut c = 'z'; //Latest char.
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//The string must start with one of the following characters.
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alt str::char_at(num, 0u) {
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'-' | '+' | '0' to '9' | '.' {}
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_ { ret none; }
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}
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//Determine if first char is '-'/'+'. Set [pos] and [neg] accordingly.
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let mut neg = false; //Sign of the result
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alt str::char_at(num, 0u) {
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'-' {
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neg = true;
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pos = 1u;
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}
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'+' {
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pos = 1u;
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}
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_ {}
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}
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//Examine the following chars until '.', 'e', 'E'
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while(pos < len) {
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let char_range = str::char_range_at(num, pos);
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c = char_range.ch;
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pos = char_range.next;
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alt c {
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'0' to '9' {
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total = total * 10f;
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total += ((c as int) - ('0' as int)) as float;
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}
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'.' | 'e' | 'E' {
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break;
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}
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_ {
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ret none;
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}
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}
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}
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if c == '.' {//Examine decimal part
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let mut decimal = 1f;
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while(pos < len) {
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let char_range = str::char_range_at(num, pos);
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c = char_range.ch;
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pos = char_range.next;
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alt c {
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'0' | '1' | '2' | '3' | '4' | '5' | '6'| '7' | '8' | '9' {
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decimal /= 10f;
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total += (((c as int) - ('0' as int)) as float)*decimal;
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}
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'e' | 'E' {
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break;
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}
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_ {
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ret none;
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}
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}
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}
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}
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if (c == 'e') | (c == 'E') {//Examine exponent
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let mut exponent = 0u;
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let mut neg_exponent = false;
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if(pos < len) {
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let char_range = str::char_range_at(num, pos);
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c = char_range.ch;
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alt c {
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'+' {
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pos = char_range.next;
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}
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'-' {
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pos = char_range.next;
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neg_exponent = true;
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}
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_ {}
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}
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while(pos < len) {
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let char_range = str::char_range_at(num, pos);
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c = char_range.ch;
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alt c {
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'0' | '1' | '2' | '3' | '4' | '5' | '6'| '7' | '8' | '9' {
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exponent *= 10u;
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exponent += ((c as uint) - ('0' as uint));
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}
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_ {
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break;
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}
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}
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pos = char_range.next;
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}
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let multiplier = pow_with_uint(10u, exponent);
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//Note: not [int::pow], otherwise, we'll quickly
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//end up with a nice overflow
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if neg_exponent {
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total = total / multiplier;
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} else {
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total = total * multiplier;
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}
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} else {
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ret none;
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}
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}
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if(pos < len) {
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ret none;
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} else {
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if(neg) {
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total *= -1f;
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}
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ret some(total);
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}
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}
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/**
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* Section: Arithmetics
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*/
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#[doc = "
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Compute the exponentiation of an integer by another integer as a float
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# Arguments
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* x - The base
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* pow - The exponent
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# Return value
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`NaN` if both `x` and `pow` are `0u`, otherwise `x^pow`
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"]
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fn pow_with_uint(base: uint, pow: uint) -> float {
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if base == 0u {
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if pow == 0u {
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ret NaN;
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}
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ret 0.;
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}
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let mut my_pow = pow;
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let mut total = 1f;
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let mut multiplier = base as float;
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while (my_pow > 0u) {
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if my_pow % 2u == 1u {
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total = total * multiplier;
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}
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my_pow /= 2u;
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multiplier *= multiplier;
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}
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ret total;
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}
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#[test]
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fn test_from_str() {
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assert from_str("3") == some(3.);
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assert from_str("3") == some(3.);
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assert from_str("3.14") == some(3.14);
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assert from_str("+3.14") == some(3.14);
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assert from_str("-3.14") == some(-3.14);
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assert from_str("2.5E10") == some(25000000000.);
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assert from_str("2.5e10") == some(25000000000.);
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assert from_str("25000000000.E-10") == some(2.5);
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assert from_str(".") == some(0.);
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assert from_str(".e1") == some(0.);
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assert from_str(".e-1") == some(0.);
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assert from_str("5.") == some(5.);
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assert from_str(".5") == some(0.5);
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assert from_str("0.5") == some(0.5);
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assert from_str("0.5") == some(0.5);
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assert from_str("0.5") == some(0.5);
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assert from_str("-.5") == some(-0.5);
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assert from_str("-.5") == some(-0.5);
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assert from_str("-5") == some(-5.);
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assert from_str("") == none;
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assert from_str("x") == none;
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assert from_str(" ") == none;
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assert from_str(" ") == none;
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assert from_str("e") == none;
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assert from_str("E") == none;
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assert from_str("E1") == none;
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assert from_str("1e1e1") == none;
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assert from_str("1e1.1") == none;
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assert from_str("1e1-1") == none;
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}
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#[test]
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fn test_positive() {
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assert(is_positive(infinity));
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assert(is_positive(1.));
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assert(is_positive(0.));
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assert(!is_positive(-1.));
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assert(!is_positive(neg_infinity));
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assert(!is_positive(1./neg_infinity));
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assert(!is_positive(NaN));
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}
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#[test]
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fn test_negative() {
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assert(!is_negative(infinity));
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assert(!is_negative(1.));
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assert(!is_negative(0.));
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assert(is_negative(-1.));
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assert(is_negative(neg_infinity));
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assert(is_negative(1./neg_infinity));
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assert(!is_negative(NaN));
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}
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#[test]
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fn test_nonpositive() {
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assert(!is_nonpositive(infinity));
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assert(!is_nonpositive(1.));
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assert(!is_nonpositive(0.));
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assert(is_nonpositive(-1.));
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assert(is_nonpositive(neg_infinity));
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assert(is_nonpositive(1./neg_infinity));
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assert(!is_nonpositive(NaN));
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}
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#[test]
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fn test_nonnegative() {
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assert(is_nonnegative(infinity));
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assert(is_nonnegative(1.));
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assert(is_nonnegative(0.));
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assert(!is_nonnegative(-1.));
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assert(!is_nonnegative(neg_infinity));
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assert(!is_nonnegative(1./neg_infinity));
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assert(!is_nonnegative(NaN));
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}
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//
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// Local Variables:
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// mode: rust
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// fill-column: 78;
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// indent-tabs-mode: nil
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// c-basic-offset: 4
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// buffer-file-coding-system: utf-8-unix
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// End:
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//
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