Operators and Concatenating Strings

String concatenation joins two or more strings together using the .. operator. This is essential for creating log messages, trade reasons, and combining text with data in your HaasScript strategies.

The Concatenation Operator

HaasScript uses two dots (..) to concatenate strings:

local firstName = "John"
local lastName = "Doe"
local fullName = firstName .. " " .. lastName

Log(fullName)  -- Outputs: John Doe

Basic Concatenation

Combining Strings

local part1 = "Hello"
local part2 = "World"
local message = part1 .. " " .. part2

Log(message)  -- Outputs: Hello World

Adding Spaces

Concatenation doesn't add spaces automatically—you must include them explicitly:

local word1 = "Hello"
local word2 = "World"

-- Wrong: No space
local message1 = word1 .. word2  -- Outputs: HelloWorld

-- Correct: Include space
local message2 = word1 .. " " .. word2  -- Outputs: Hello World

Automatic Type Conversion

HaasScript automatically converts numbers to strings during concatenation:

local rsi = 25.5
local message = "RSI value: " .. rsi

Log(message)  -- Outputs: RSI value: 25.5

This works with all numeric types:

local price = 45000
local percentage = 2.5
local count = 100

local message = "Price: " .. price .. ", Change: " .. percentage .. "%, Trades: " .. count
Log(message)  -- Outputs: Price: 45000, Change: 2.5%, Trades: 100

Trading Use Cases

Trade Reasons with Indicator Values

local rsi = RSI(ClosePrices(), 14)

if rsi < 30 then
    DoLong("RSI oversold: " .. rsi)
elseif rsi > 70 then
    DoShort("RSI overbought: " .. rsi)
end

Combining Multiple Indicators

local rsi = RSI(ClosePrices(), 14)
local macd = MACD(ClosePrices(), 12, 26, 9)

local message = "RSI: " .. rsi .. " | MACD: " .. macd
Log(message)

Dynamic Labels

local market = BaseCurrency() .. "_" .. QuoteCurrency()
local strategy = "RSI Strategy"
local timeframe = "15m"

local label = strategy .. " - " .. market .. " - " .. timeframe
Log(label)

Price and Percentage Messages

local entryPrice = 45000
local currentPrice = 46200
local profitPercent = ((currentPrice - entryPrice) / entryPrice) * 100

local message = "Entry: " .. entryPrice .. " | Current: " .. currentPrice .. " | Profit: " .. profitPercent .. "%"
Log(message)

Position Status

local hasLong = HasLongPosition()
local entryPrice = GetEntryPrice()

if hasLong then
    local message = "Long position at " .. entryPrice
    Log(message)
end

Common Mistakes

Using the Wrong Operator

local text1 = "Hello"
local text2 = "World"

-- Wrong: Using + (only for numbers)
local message = text1 + " " + text2  -- Error!

-- Correct: Using ..
local message = text1 .. " " .. text2

Forgetting Spaces

local firstName = "John"
local lastName = "Doe"

-- Wrong: No space
local name = firstName .. lastName  -- Outputs: JohnDoe

-- Correct: Add space
local name = firstName .. " " .. lastName  -- Outputs: John Doe

Concatenating with Nil

local value = nil  -- Undefined variable

-- Error: Cannot concatenate nil
local message = "Value: " .. value

-- Correct: Check for nil first
if value ~= nil then
    local message = "Value: " .. value
else
    local message = "Value: (not set)"
end

Concatenating Booleans

local isActive = true

-- Error: Cannot concatenate boolean directly
local message = "Status: " .. isActive

-- Correct: Convert to string
local message = "Status: " .. tostring(isActive)
Log(message)  -- Outputs: Status: true

Multi-Line Concatenation

Build longer messages by chaining the .. operator:

local rsi = RSI(ClosePrices(), 14)
local macd = MACD(ClosePrices(), 12, 26, 9)
local price = ClosePrices()

local message = "=== Analysis ===" .. "\n" ..
                "Price: " .. price .. "\n" ..
                "RSI: " .. rsi .. "\n" ..
                "MACD: " .. macd

Log(message)

Building Messages Conditionally

Add information to a message based on conditions:

local rsi = RSI(ClosePrices(), 14)
local message = "RSI: " .. rsi

if rsi < 30 then
    message = message .. " (OVERSOLD)"
elseif rsi > 70 then
    message = message .. " (OVERBOUGHT)"
end

Log(message)  -- Outputs: RSI: 25.5 (OVERSOLD)

Best Practices

1. Use .. for concatenation - not + or other operators
2. Add spaces manually - concatenation doesn't add them automatically
3. Check for nil - before concatenating potentially empty variables
4. Convert booleans - use tostring() for boolean values
5. Use parentheses for complex concatenation to improve clarity
6. Build incrementally - add parts to a message step by step
7. Use meaningful text - clear, descriptive labels in log messages

Summary

• Operator: .. joins strings together
• Automatic conversion: Numbers convert to strings automatically
• Manual spaces: You must add spaces explicitly
• Type conversion needed: Booleans and nil require explicit conversion
• Common uses: Log messages, trade reasons, dynamic labels
• Avoid mistakes: Use correct operator, check for nil, handle types properly

String concatenation is simple but essential for creating informative messages in your trading strategies. Master the .. operator to communicate what your strategy is doing and why.