feat(std): std math functions. (amber-lang#384)

* feat(std): more rounding `std` math functions.

implements the math functions suggested in amber-lang#328

* feat(std): `abs` function

* fix(shellcheck)

src/std/math.ab

@@ -3,3 +3,27 @@ pub fun sum(list: [Num]): Num {
     return unsafe $echo "{list}" | awk '\{s=0; for (i=1; i<=NF; i++) s+=\$i; print s}'$ as Num
 }
 
+/// Returns the number rounded to the nearest integer
+#[allow_absurd_cast]
+pub fun round(number: Num): Num {
+    return unsafe $printf "%0.f" "{number}"$ as Num
+}
+
+/// Returns the largest integer less than or equal to the number
+#[allow_absurd_cast]
+pub fun floor(number: Num): Num {
+    return unsafe $echo "{number}" | awk '\{printf "%d", (\$1 < 0 ? int(\$1) - 1 : int(\$1))}'$ as Num
+}
+
+/// Returns the smallest integer greater than or equal to the number
+#[allow_absurd_cast]
+pub fun ceil(number: Num): Num {
+    return floor(number) + 1
+}
+
+/// Returns the absolute value of the number
+#[allow_absurd_cast]
+pub fun abs(number: Num): Num {
+    if number < 0: return -number
+    return number
+}

src/tests/stdlib/abs.ab

@@ -0,0 +1,10 @@
+import * from "std/math"
+
+// Output 
+// 1
+// 1
+
+main {
+    echo abs(1);
+    echo abs(-1);
+}

src/tests/stdlib/ceil.ab

@@ -0,0 +1,10 @@
+import * from "std/math"
+
+// Output
+// 2
+// -1
+
+main {
+    echo ceil(1.1);
+    echo ceil(-1.9);
+}

src/tests/stdlib/floor.ab

@@ -0,0 +1,10 @@
+import * from "std/math"
+
+// Output
+// 1
+// -2
+
+main {
+    echo floor(1.9);
+    echo floor(-1.1);
+}

src/tests/stdlib/round.ab

@@ -0,0 +1,14 @@
+import * from "std/math"
+
+// Output
+// 1
+// 2
+// -1
+// -2
+
+main {
+    echo round(1.1);
+    echo round(1.5);
+    echo round(-1.1);
+    echo round(-1.5);
+}