gohugoio/hugo · error

must provide at least two numbers

Error message

must provide at least two numbers

What it means

Defined as errMustTwoNumbersError (tpl/math/math.go:30) and returned by doArithmetic when fewer than two inputs are supplied. It backs the variadic Add, Sub, Mul, and Div functions, which require at least two operands to perform a binary operation.

Source

Thrown at tpl/math/math.go:30

// limitations under the License.

// Package math provides template functions for mathematical operations.
package math

import (
	"errors"
	"fmt"
	"math"
	"math/rand"
	"reflect"

	_math "github.com/gohugoio/hugo/common/math"
	"github.com/gohugoio/hugo/deps"
	"github.com/spf13/cast"
)

var (
	errMustTwoNumbersError = errors.New("must provide at least two numbers")
	errMustOneNumberError  = errors.New("must provide at least one number")
)

// New returns a new instance of the math-namespaced template functions.
func New(d *deps.Deps) *Namespace {
	return &Namespace{
		d: d,
	}
}

// Namespace provides template functions for the "math" namespace.
type Namespace struct {
	d *deps.Deps
}

// Abs returns the absolute value of n.
func (ns *Namespace) Abs(n any) (float64, error) {
	af, err := cast.ToFloat64E(n)

View on GitHub (pinned to 52c9bd7908)

Solutions

1. Supply at least two numeric arguments: {{ math.Add 1 2 }}.
2. For increments, pass an explicit second operand: {{ math.Add .Count 1 }}.
3. When piping, ensure the piped value plus at least one positional arg are both present: {{ math.Add .X 1 }} with .X on the left of the pipe.
4. Use math.Sum (which accepts one or more via slices) if you need single-operand summation behavior.

Example fix

// before
{{ $total := math.Add .Price }}

// after
{{ $total := math.Add .Price .Tax }}

// Provide at least two operands to Add/Sub/Mul/Div:
{{ math.Add .Price .Tax }}
// For single-operand sums over slices, use math.Sum instead:
{{ math.Sum (slice 1 2 3) }}

// Go caller of doArithmetic-backed functions:
func enoughOperands(inputs []any) bool { return len(inputs) >= 2 }

When it happens

Trigger: Calling {{ math.Add 5 }} (one arg), {{ math.Mul }} (zero args), or piping nothing into {{ .X | math.Add }} so only one value arrives. Sub/Div are not commutative so a single operand is ambiguous and rejected.

Common situations: Piping into math.Add expecting it to behave like an increment; forgetting the second operand in a template; refactoring a list and ending up with a single-element slice piped to a variadic op.

Related errors

• can't divide the value by 0
• invalid number of arguments to Seq
• invalid arguments to Seq
• both count and seq must be provided
• complement needs at least two arguments

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/7ae21ae69fecd589. Report an issue: GitHub.