Add some basic math interpolation functions

Support the following math functions for interpolation:

* ceil
* floor
* max
* min

Fixes hashicorp#7409

config/interpolate_funcs.go

@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"math"
 	"net"
 	"regexp"
 	"sort"
@@ -54,6 +55,7 @@ func Funcs() map[string]ast.Function {
 		"base64decode": interpolationFuncBase64Decode(),
 		"base64encode": interpolationFuncBase64Encode(),
 		"base64sha256": interpolationFuncBase64Sha256(),
+		"ceil":         interpolationFuncCeil(),
 		"cidrhost":     interpolationFuncCidrHost(),
 		"cidrnetmask":  interpolationFuncCidrNetmask(),
 		"cidrsubnet":   interpolationFuncCidrSubnet(),
@@ -63,6 +65,7 @@ func Funcs() map[string]ast.Function {
 		"distinct":     interpolationFuncDistinct(),
 		"element":      interpolationFuncElement(),
 		"file":         interpolationFuncFile(),
+		"floor":        interpolationFuncFloor(),
 		"format":       interpolationFuncFormat(),
 		"formatlist":   interpolationFuncFormatList(),
 		"index":        interpolationFuncIndex(),
@@ -72,8 +75,10 @@ func Funcs() map[string]ast.Function {
 		"list":         interpolationFuncList(),
 		"lower":        interpolationFuncLower(),
 		"map":          interpolationFuncMap(),
+		"max":          interpolationFuncMax(),
 		"md5":          interpolationFuncMd5(),
 		"merge":        interpolationFuncMerge(),
+		"min":          interpolationFuncMin(),
 		"uuid":         interpolationFuncUUID(),
 		"replace":      interpolationFuncReplace(),
 		"sha1":         interpolationFuncSha1(),
@@ -387,6 +392,66 @@ func interpolationFuncFormat() ast.Function {
 	}
 }
 
+// interpolationFuncMax returns the maximum of the numeric arguments
+func interpolationFuncMax() ast.Function {
+	return ast.Function{
+		ArgTypes:     []ast.Type{ast.TypeFloat},
+		ReturnType:   ast.TypeFloat,
+		Variadic:     true,
+		VariadicType: ast.TypeFloat,
+		Callback: func(args []interface{}) (interface{}, error) {
+			max := args[0].(float64)
+
+			for i := 1; i < len(args); i++ {
+				max = math.Max(max, args[i].(float64))
+			}
+
+			return max, nil
+		},
+	}
+}
+
+// interpolationFuncMin returns the minimum of the numeric arguments
+func interpolationFuncMin() ast.Function {
+	return ast.Function{
+		ArgTypes:     []ast.Type{ast.TypeFloat},
+		ReturnType:   ast.TypeFloat,
+		Variadic:     true,
+		VariadicType: ast.TypeFloat,
+		Callback: func(args []interface{}) (interface{}, error) {
+			min := args[0].(float64)
+
+			for i := 1; i < len(args); i++ {
+				min = math.Min(min, args[i].(float64))
+			}
+
+			return min, nil
+		},
+	}
+}
+
+// interpolationFuncCeil returns the the least integer value greater than or equal to the argument
+func interpolationFuncCeil() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeFloat},
+		ReturnType: ast.TypeInt,
+		Callback: func(args []interface{}) (interface{}, error) {
+			return int(math.Ceil(args[0].(float64))), nil
+		},
+	}
+}
+
+// interpolationFuncFloorreturns returns the greatest integer value less than or equal to the argument
+func interpolationFuncFloor() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeFloat},
+		ReturnType: ast.TypeInt,
+		Callback: func(args []interface{}) (interface{}, error) {
+			return int(math.Floor(args[0].(float64))), nil
+		},
+	}
+}
+
 func interpolationFuncZipMap() ast.Function {
 	return ast.Function{
 		ArgTypes: []ast.Type{

config/interpolate_funcs_test.go

@@ -222,6 +222,150 @@ func TestInterpolateFuncList(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncMax(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${max()}`,
+				nil,
+				true,
+			},
+
+			{
+				`${max("")}`,
+				nil,
+				true,
+			},
+
+			{
+				`${max(-1, 0, 1)}`,
+				"1",
+				false,
+			},
+
+			{
+				`${max(1, 0, -1)}`,
+				"1",
+				false,
+			},
+
+			{
+				`${max(-1, -2)}`,
+				"-1",
+				false,
+			},
+
+			{
+				`${max(-1)}`,
+				"-1",
+				false,
+			},
+		},
+	})
+}
+
+func TestInterpolateFuncMin(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${min()}`,
+				nil,
+				true,
+			},
+
+			{
+				`${min("")}`,
+				nil,
+				true,
+			},
+
+			{
+				`${min(-1, 0, 1)}`,
+				"-1",
+				false,
+			},
+
+			{
+				`${min(1, 0, -1)}`,
+				"-1",
+				false,
+			},
+
+			{
+				`${min(-1, -2)}`,
+				"-2",
+				false,
+			},
+
+			{
+				`${min(-1)}`,
+				"-1",
+				false,
+			},
+		},
+	})
+}
+
+func TestInterpolateFuncFloor(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${floor()}`,
+				nil,
+				true,
+			},
+
+			{
+				`${floor("")}`,
+				nil,
+				true,
+			},
+
+			{
+				`${floor("-1.3")}`, // there appears to be a AST bug where the parsed argument ends up being -1 without the "s
+				"-2",
+				false,
+			},
+
+			{
+				`${floor(1.7)}`,
+				"1",
+				false,
+			},
+		},
+	})
+}
+
+func TestInterpolateFuncCeil(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${ceil()}`,
+				nil,
+				true,
+			},
+
+			{
+				`${ceil("")}`,
+				nil,
+				true,
+			},
+
+			{
+				`${ceil(-1.8)}`,
+				"-1",
+				false,
+			},
+
+			{
+				`${ceil(1.2)}`,
+				"2",
+				false,
+			},
+		},
+	})
+}
+
 func TestInterpolateFuncMap(t *testing.T) {
 	testFunction(t, testFunctionConfig{
 		Cases: []testFunctionCase{

website/source/docs/configuration/interpolation.html.md

@@ -89,6 +89,9 @@ The supported built-in functions are:
     **This is not equivalent** of `base64encode(sha256(string))`
     since `sha256()` returns hexadecimal representation.
 
+  * `ceil(float)` - Returns the the least integer value greater than or equal
+      to the argument.
+
   * `cidrhost(iprange, hostnum)` - Takes an IP address range in CIDR notation
     and creates an IP address with the given host number. For example,
     ``cidrhost("10.0.0.0/8", 2)`` returns ``10.0.0.2``.
@@ -137,6 +140,9 @@ The supported built-in functions are:
       module, you generally want to make the path relative to the module base,
       like this: `file("${path.module}/file")`.
 
+  * `floor(float)` - Returns the greatest integer value less than or equal to
+      the argument
+
   * `format(format, args, ...)` - Formats a string according to the given
       format. The syntax for the format is standard `sprintf` syntax.
       Good documentation for the syntax can be [found here](https://golang.org/pkg/fmt/).
@@ -197,11 +203,15 @@ The supported built-in functions are:
     * `map("hello", "world")`
     * `map("us-east", list("a", "b", "c"), "us-west", list("b", "c", "d"))`
 
+  * `max(float1, float2, ...)` - Returns the largest of the floats.
+
   * `merge(map1, map2, ...)` - Returns the union of 2 or more maps. The maps
 	are consumed in the order provided, and duplicate keys overwrite previous
 	entries.
 	* `${merge(map("a", "b"), map("c", "d"))}` returns `{"a": "b", "c": "d"}`
 
+  * `min(float1, float2, ...)` - Returns the smallest of the floats.
+
   * `md5(string)` - Returns a (conventional) hexadecimal representation of the
     MD5 hash of the given string.