Helper API refactor (#40)

* api cleaup

* updates

* wtf

* updates

* snapshot.

* tweaks

* snapshot

* api tweaks.

* updates

* updates

* updates

* changes.

* updates

* updates

* sequence => seq

* dont need to use curl, just using wget

* fixing examples

seq/linear.go

@@ -0,0 +1,73 @@
+package seq
+
+// Range returns the array values of a linear seq with a given start, end and optional step.
+func Range(start, end float64) []float64 {
+	return Seq{NewLinear().WithStart(start).WithEnd(end).WithStep(1.0)}.Array()
+}
+
+// RangeWithStep returns the array values of a linear seq with a given start, end and optional step.
+func RangeWithStep(start, end, step float64) []float64 {
+	return Seq{NewLinear().WithStart(start).WithEnd(end).WithStep(step)}.Array()
+}
+
+// NewLinear returns a new linear generator.
+func NewLinear() *Linear {
+	return &Linear{step: 1.0}
+}
+
+// Linear is a stepwise generator.
+type Linear struct {
+	start float64
+	end   float64
+	step  float64
+}
+
+// Start returns the start value.
+func (lg Linear) Start() float64 {
+	return lg.start
+}
+
+// End returns the end value.
+func (lg Linear) End() float64 {
+	return lg.end
+}
+
+// Step returns the step value.
+func (lg Linear) Step() float64 {
+	return lg.step
+}
+
+// Len returns the number of elements in the seq.
+func (lg Linear) Len() int {
+	if lg.start < lg.end {
+		return int((lg.end-lg.start)/lg.step) + 1
+	}
+	return int((lg.start-lg.end)/lg.step) + 1
+}
+
+// GetValue returns the value at a given index.
+func (lg Linear) GetValue(index int) float64 {
+	fi := float64(index)
+	if lg.start < lg.end {
+		return lg.start + (fi * lg.step)
+	}
+	return lg.start - (fi * lg.step)
+}
+
+// WithStart sets the start and returns the linear generator.
+func (lg *Linear) WithStart(start float64) *Linear {
+	lg.start = start
+	return lg
+}
+
+// WithEnd sets the end and returns the linear generator.
+func (lg *Linear) WithEnd(end float64) *Linear {
+	lg.end = end
+	return lg
+}
+
+// WithStep sets the step and returns the linear generator.
+func (lg *Linear) WithStep(step float64) *Linear {
+	lg.step = step
+	return lg
+}