add std.math.big.Int.fitsInTwosComp

andrewrk · andrewrk · commit 99153ac0aa39 · 2018-07-22T10:58:45.000-04:00
so that we can pass runtime-known values
diff --git a/std/math/big/int.zig b/std/math/big/int.zig
@@ -150,16 +150,20 @@ pub const Int = struct {
         return bits;
     }
 
-    pub fn fits(self: Int, comptime T: type) bool {
+    pub fn fitsInTwosComp(self: Int, is_signed: bool, bit_count: usize) bool {
         if (self.eqZero()) {
             return true;
         }
-        if (!T.is_signed and !self.positive) {
+        if (!is_signed and !self.positive) {
             return false;
         }
 
-        const req_bits = self.bitCountTwosComp() + @boolToInt(self.positive and T.is_signed);
-        return T.bit_count >= req_bits;
+        const req_bits = self.bitCountTwosComp() + @boolToInt(self.positive and is_signed);
+        return bit_count >= req_bits;
+    }
+
+    pub fn fits(self: Int, comptime T: type) bool {
+        return self.fitsInTwosComp(T.is_signed, T.bit_count);
     }
 
     // Returns the approximate size of the integer in the given base. Negative values accomodate for

Original file line number	Diff line number	Diff line change
`@@ -150,16 +150,20 @@ pub const Int = struct {`
`150`	`150`	`return bits;`
`151`	`151`	`}`
`152`	`152`
`153`		`- pub fn fits(self: Int, comptime T: type) bool {`
	`153`	`+ pub fn fitsInTwosComp(self: Int, is_signed: bool, bit_count: usize) bool {`
`154`	`154`	`if (self.eqZero()) {`
`155`	`155`	`return true;`
`156`	`156`	`}`
`157`		`- if (!T.is_signed and !self.positive) {`
	`157`	`+ if (!is_signed and !self.positive) {`
`158`	`158`	`return false;`
`159`	`159`	`}`
`160`	`160`
`161`		`- const req_bits = self.bitCountTwosComp() + @boolToInt(self.positive and T.is_signed);`
`162`		`- return T.bit_count >= req_bits;`
	`161`	`+ const req_bits = self.bitCountTwosComp() + @boolToInt(self.positive and is_signed);`
	`162`	`+ return bit_count >= req_bits;`
	`163`	`+ }`
	`164`	`+`
	`165`	`+ pub fn fits(self: Int, comptime T: type) bool {`
	`166`	`+ return self.fitsInTwosComp(T.is_signed, T.bit_count);`
`163`	`167`	`}`
`164`	`168`
`165`	`169`	`// Returns the approximate size of the integer in the given base. Negative values accomodate for`