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functions.go
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package main
import (
"fmt"
"math"
"github.com/Knetic/govaluate"
)
var evalFunctions = map[string]govaluate.ExpressionFunction{
"strlen": func(args ...interface{}) (interface{}, error) {
length := len(args[0].(string))
return (float64)(length), nil
},
// log(100) = 2
// log(4, 2) = 2
"log": func(args ...interface{}) (interface{}, error) {
if len(args) > 2 {
return nil, fmt.Errorf("Too many arguments to log")
}
if len(args) < 1 {
return nil, fmt.Errorf("Too few arguments to log")
}
var argsFloat64 [2]float64
for i := range args {
switch args[i].(type) {
case float64:
argsFloat64[i] = args[i].(float64)
case bool:
if args[i].(bool) {
argsFloat64[i] = 1
} else {
argsFloat64[i] = 0
}
case string:
return nil, fmt.Errorf("Argument %d is string to log", i)
}
}
val := math.Log10(argsFloat64[0])
if len(args) > 1 {
val /= math.Log10(argsFloat64[1])
}
return val, nil
},
}