refactor: move ConstructPatterns into compiler package

ConstructPatterns was never used except during compilation, so it
makes sense to have it closer where it is used. We could consider
making it even private function, as the pattern table construction
is quite specific to how compiler compiles and probably not that
reusable elsewhere.

vm/compiler/compiler.go

@@ -91,7 +91,7 @@ func (com *Compiler) Song(song *sointu.Song) (map[string]string, error) {
 	if err != nil {
 		return nil, fmt.Errorf(`could not encode patch: %v`, err)
 	}
-	patterns, sequences, err := vm.ConstructPatterns(song)
+	patterns, sequences, err := ConstructPatterns(song)
 	if err != nil {
 		return nil, fmt.Errorf(`could not encode song: %v`, err)
 	}

vm/compiler/patterns.go

@@ -1,4 +1,4 @@
-package vm
+package compiler
 
 import (
 	"errors"

vm/compiler/patterns_test.go

@@ -1,11 +1,11 @@
-package vm_test
+package compiler_test
 
 import (
 	"reflect"
 	"testing"
 
 	"github.com/vsariola/sointu"
-	"github.com/vsariola/sointu/vm"
+	"github.com/vsariola/sointu/vm/compiler"
 )
 
 func TestPatternReusing(t *testing.T) {
@@ -22,7 +22,7 @@ func TestPatternReusing(t *testing.T) {
 			}},
 		},
 	}
-	patterns, sequences, err := vm.ConstructPatterns(&song)
+	patterns, sequences, err := compiler.ConstructPatterns(&song)
 	if err != nil {
 		t.Fatalf("erorr constructing patterns: %v", err)
 	}
@@ -49,7 +49,7 @@ func TestUnnecessaryHolds(t *testing.T) {
 				Order:    []int{0, 1},
 			}}},
 	}
-	patterns, sequences, err := vm.ConstructPatterns(&song)
+	patterns, sequences, err := compiler.ConstructPatterns(&song)
 	if err != nil {
 		t.Fatalf("erorr constructing patterns: %v", err)
 	}
@@ -77,7 +77,7 @@ func TestDontCares(t *testing.T) {
 			}},
 		},
 	}
-	patterns, sequences, err := vm.ConstructPatterns(&song)
+	patterns, sequences, err := compiler.ConstructPatterns(&song)
 	if err != nil {
 		t.Fatalf("erorr constructing patterns: %v", err)
 	}