Add 'bin' and 'oct', closes #289

Author: sharkdp

book/src/number-notation.md

@@ -17,3 +17,16 @@ Numbers in Numbat can be written in the following forms:
     * `0x2A` — Hexadecimal
     * `0o52` — Octal
     * `0b101010` — Binary
+
+## Convert numbers to other bases
+
+You can use the `bin`, `oct`, and `hex` functions to convert numbers to binary, octal, and hexadecimal bases, respectively.
+As with any other function, you can call those using `hex(2^16 - 1)`, but it's often more convenient to use the `… // hex`
+convention to convert a number.
+
+Examples:
+```nbt
+0xffee // bin
+42 // oct
+2^16 - 1 // hex
+```

examples/prelude_tests.nbt

@@ -73,6 +73,21 @@ assert(str_replace("xxx", "x", "yY") == "yYyYyY")
 
 assert(str_repeat("xy", 3) == "xyxyxy")
 
+assert(bin(0b0) == "0b0")
+assert(bin(0b1) == "0b1")
+assert(bin(0b10) == "0b10")
+assert(bin(0b11) == "0b11")
+assert(bin(0b10101010101010101010101010101010) == "0b10101010101010101010101010101010")
+assert(bin(-0b11110000) == "-0b11110000")
+
+assert(oct(0o0) == "0o0")
+assert(oct(0o1) == "0o1")
+assert(oct(0o7) == "0o7")
+assert(oct(0o10) == "0o10")
+assert(oct(0o77) == "0o77")
+assert(oct(0o12345670) == "0o12345670")
+assert(oct(-0o12345670) == "-0o12345670")
+
 assert(hex(0x0) == "0x0")
 assert(hex(0x1) == "0x1")
 assert(hex(0x9) == "0x9")

numbat/modules/core/strings.nbt

@@ -30,12 +30,32 @@ fn str_repeat(a: String, n: Scalar) -> String =
     then str_append(a, str_repeat(a, n - 1))
     else ""
 
-fn hex_digit(x: Scalar) -> String =
+fn _bin_digit(x: Scalar) -> String =
+  chr(48 + mod(x, 2))
+
+fn _oct_digit(x: Scalar) -> String =
+  chr(48 + mod(x, 8))
+
+fn _hex_digit(x: Scalar) -> String =
     if mod(x, 16) < 10 then chr(48 + mod(x, 16)) else chr(97 + mod(x, 16) - 10)
 
+fn bin(x: Scalar) -> String =
+  if x < 0
+    then "-{bin(-x)}"
+    else if x < 2
+      then "0b{chr(48 + x)}"
+      else str_append(bin(floor(x / 2)), _bin_digit(mod(x, 2)))
+
+fn oct(x: Scalar) -> String =
+  if x < 0
+    then "-{oct(-x)}"
+    else if x < 8
+      then "0o{chr(48 + x)}"
+      else str_append(oct(floor(x / 8)), _oct_digit(x))
+
 fn hex(x: Scalar) -> String =
-    if x < 0
-      then "-{hex(-x)}"
-      else if floor(x / 16) == 0
-        then str_append("0x", hex_digit(x))
-        else str_append(hex(floor(x / 16)), hex_digit(x))
+  if x < 0
+    then "-{hex(-x)}"
+    else if floor(x / 16) == 0
+      then str_append("0x", _hex_digit(x))
+      else str_append(hex(floor(x / 16)), _hex_digit(x))